1. Field
The present invention relates to an encapsulation cap and a display device including the same. Particularly, the present invention relates to an encapsulation cap having a structure which has a reinforced strength and is not modified although a thickness of a workpiece is decreased and a display device including the same.
2. Background
An organic light-emitting device, one of the display devices, is a device using organic electroluminescence. Organic electroluminescence is a phenomenon that excitons are formed in an (low molecular or high molecular) organic material thin film by re-combining holes injected through an anode with electrons injected through a cathode, and a light of specific wavelength is generated by energy of the formed excitons.
The organic light-emitting device using the above a phenomenon has the basic structure as illustrated in FIG. 1. The organic light-emitting device comprises a glass substrate 200, an indium tin oxide film 102 disposed on the glass substrate 200 and acting as the anode electrode (hereinafter, referred to as “anode electrode”), an insulating layer and an organic light-emitting layer 103 disposed sequentially on the anode electrode and a metal layer 104 disposed on the organic light-emitting layer and acting as the cathode electrode (hereinafter, referred to as “cathode electrode”).
FIG. 2 is a plane view of the organic light-emitting device shown in FIG. 1, In FIG. 2, the organic light-emitting device to which a cap is not attached is illustrated. Also, in FIG. 2, an active area 100 consisting of the structural elements described above is shown in the shape of the box.
As shown in FIG. 1 and FIG. 2, in a process of forming the anode electrodes 102 and the cathode electrodes 104, data lines 111 and scan lines 110a and 110b are formed on a periphery of the active area 100 and connected to the anode electrodes 102 and the cathode electrode 104 in the active area 100, respectively.
In FIG. 1, on the other hand, the reference numeral “108” which is not illustrated indicates a moisture absorbing material layer (hereinafter, referred to as “getter”) attached on an inner surface of the cap 106 through an adhesive 107, and the reference numeral “W” indicates a wall formed for separating the cathode electrodes 104.
Here, a cap 106 is attached on a cap-attaching region 112 of the substrate 200 defined as an outer region of the active area 100 through an adhesive 106A (hereinafter, referred to as “sealant”). The cap 106 is used for isolating and protecting the structural elements in the active area 100 from an external environment such as moisture, light and the like and is mainly made from metal material.
An entire thickness (height) of the organic light-emitting device having the structure as described above includes a thickness of the substrate 200, a thickness of the sealant 106A applied on the substrate 200, a thickness of the cap 106 and a thickness of a reflective film (not shown) attached on a lower surface of the substrate 200 which is opposed to a surface on which the structural elements are disposed.
For example, thicknesses of the members constituting the organic light-emitting device with a thickness of 1.83 mm are as follows:
Glass substrate (200): 0.7 mm
Sealant (106A): 0.03 mm
Reflective film: 0.2 mm
Cap (106): 0.9 mm
(not a thickness of the workpiece, but an entire thickness of the cap)
In order to slim down the organic light-emitting device, the study has been conducted for reducing a thickness of each structural member, however, there are limitations to reduce a thickness of the sealant 106A applied on the substrate for attaching the cap and a thickness of the reflective film due to the characteristics of the material thereof.
Accordingly, an entire thickness of the organic light-emitting device can be reduced by reducing thicknesses of the substrate 200 and the cap 106. In particular, it is more effective to reduce a thickness of the cap 106 which has more room than the glass substrate 200 in terms of the dimension and the strength.
FIG. 3 is a sectional view of the cap according to the related art. For example, a cap 106-1 with an entire thickness T1 of 0.9 mm is made from a metal workpiece having a thickness t1 of 0.3 mm. A space S1 having a height of approximately 0.6 mm is formed in the cap 106-1 due to a difference between a central portion C-1 and an attaching portion B-1 to be attached to an attaching region (112 in FIG. 2) of the substrate.
If the cap 106-1 shown in FIG. 3 is made from the metal workpiece having a thickness which is thin by approximately 0.1 mm, that is, having a thickness of 0.2 mm, an entire height T1 of the cap 106-1 can be reduced by approximately 0.2 mm while the same height of the inner space S1 is maintained.
On the other hand, there is a solution that a height of the inner space S1 is reduced to reduce an entire height T1 of the cap 106-1. However, there is a limit to reduce a height of the inner space S1 of the cap 106-1 if the special regard will be paid to the fact that a distance between the getter 108 (in FIG. 1) attached to an inner surface of the central portion C1 of the cap 106-1 and the structural element such as the wall W (in FIG. 1) or the cathode electrode 104 should be maintained to some degree.
FIG. 4 is a sectional view of the cap having another structure, according to the related art. The cap 106-2 shown in FIG. 4 has a first space S2 formed on a central portion C-2 and a second space S2-1 formed on a central portion of the first space S2. The getter 108 (in FIG. 1) is attached to the central portion C-2 corresponding to the second space S2-1. Due to the second space S2-1, the cap 106-2 has a structure in which some region of the central portion C-2 is protruded with a certain height.
If the cap 106-2 having the structure as described above is made from the metal workpiece having a thickness which is thin by approximately 0.1 mm, that is, having a thickness of 0.2 mm, an entire height T2 of the cap 106-2 can be reduced by approximately 0.2 mm while the same height of the inner space S1 and S2 is maintained.
As described above, in order to reduce a thickness of the organic light-emitting area, that is, an entire thickness of the cap 106-1 or 106-2, it is most preferred to reduce a thickness of the workpiece (for example, the metal sheet) used for manufacturing the cap.
However, if the cap 106-1 or 106-2 is made from the metal sheet having a reduced thickness, it is difficult to obtain a desired shape and a specification of the cap. That is, a deformation such as a deflection is generated on a large portion (that is, C-1 in FIG. 3 and C-2 in FIG. 4 to which the getter is attached) of the cap with a thin thickness. Accordingly, there is a strong possibility that the getter is contacted with the structural elements of the device. Such contact between the getter and the structural element increases the possibility that a line fail of the cathode electrodes is generated, consequently an inferiority of the organic light-emitting device is caused by the above contact
In particular, the metal cap 106-1 or 106-2 made from the thin metal sheet has a weak structural strength, and a distortion caused by a spring back phenomenon (an elastic back caused by removing a load after the plastic deformation and an elastic deformation generated after bending) is also generated on the cap, and so a function of the cap can undergo the serious influence.